Circuit interrupter



Dec. 26, 1939. J. M. WALLACE CIRCUIT INTERRUPTER Filed NOV. 12, 1937INVENTOR Jqme 5. /1/7. l/l/a//ac.,a

BY f 'Patented Dec. 26, 1939 PATENT OFFICE CIRCUIT INTERRUPTEB James M.

Wallace, Braddock, Pa., assignor to Westinghouse Electric &Manufacturing Company, East Pittsburgh, Pa., a

Pennsylvania corporation of Application November 12, 1937, Serial No.174,194

11 Claims.

My invention relates to circuit interrnpters and particularly toexpulsion type devices wherein the arc is drawn in a restricted passagehaving a material therealong which gives oil gas when acted upon by thearc. This gas iiows through the arc and out one end of the passage tocarry away the ionized arc products. A closed kcooling chamber orcondenser is placed over the end of the arc passage to receive the gasesgiven oi.

This invention is an improvement in the condenser part of such a circuitinterrupter and makes it possible to interrupt higher short-circuitcurrents than was possible with the prior art devices, such as shown inSlepian Patent No. 2,077,276, issued April 13, 1937', and Rawlins PatentNo. 2,082,028, issued June l, 1937, both assigned to the assignee ofthis application. It is an object of my invention to provide an entirelyenclosed circuit interrupter which is capable of interrupting heavyshort-circuit currents. This is accomplished by providing the coolingmeans in the closed chamber with a tapered opening therethrough so asyto make use of the kinetic energy of theowing gas to distribute the gasquickly and uniformly throughout the condensing chamber and takefulladvantage of the cooling capacity of all parts of the condenser.

In one form of a device embodying my invention, the condenser comprisesa plurality of spaced metal plates or washers having a central openingtherethrough. The holes through the plates vary in size from a largeopening in the plates adjacent the end of the arc passage to a smallsize at the opposite end of the structure. The large opening at the endof the cooling structure adjacent the arc passage permits the gasesilowing out of the arc passage to ow freely without substantialobstruction. This makes it possible to take full advantage of theexpulsion action to carry away the ionized gas in the arc passage sothat the arc is quickly extinguished.

'I'he fact that the opening through the plates is tapered provides auniform distribution of the gas throughout all parts of the condenserinstead of permitting the gas to iiow all the way through the stack ofplates until it hits the closed end ind then be deilected back only intothe lowermost plates in the stack. By using plates having openings ofvarious sizes, the. edge `portions around the openings which projectbeyond the edges of the plates above serve to catch the outiowing gasand deilect it into the spaces between the plates, thus using thekinetic energy of the gas to distribute it uniformly among the plates.

(Cl. 20D-149) In the older types of devices with openings oi uniformsize, the gas diffused between the plates solely because of pressurebuilt up in the chamber. 'I'his slowed down the condensing action and isundesirable since the building up of pressure in the condenser retardsthe expulsive ilow of gas through the arc, and, therefore, reduced thearc extinguishing ability of the device.

In a preferredform of my invention, the arc passage is lined with boricacid, `which gives of! water vapor or superheated steam which is quicklycondensed as soon as `it comes in contact with the relatively coolsurfaces` of the metallic plates in the condenser. This relieves thepressure within the device and permits the gas to flow through the arcwith an expulsion action so as to quickly extinguish the arc.

`Laboratory tests on a circuit interrupter embodying my invention showthat it will successfully interrupt a short-circuit current ci 67,000peak amperes at 7500 volts, whereas a circuit interrupter using acondenser of the older design failed under the same circuit conditionsat 37,000 peak amperes. By using the condenser of my invention, theinterrupting ability of the fuse is raised almost to that obtainablefrom a fuse without a condenser where the gas may ilow freely out theopen end of the arc passage. At the same time, all of the advantages ofan entirely enclosed fuse are retained. There is no llame or ionized gasemitted from the fuse, which makes it possible to mount the fuse inrestricted spaces indoors where the emission of' hot ionized gases mightcause flashover between the conducting parts of adjacent apparatus. Theuse of an entirely enclosed condenser also greatly reduces the amount ofnoise present when heavy shortcircuit currents are interrupted.

These-and other objects and advantages of my invention will be morefully apparent from the following description of the drawing whichillustrates a specific embodiment of the invention. In the drawing:

Figure 1 is a view, partly in cross-section and partly in elevation, ofone form of my invention;

Fig. 2 is an enlarged transverse cross-sectional view through thecondenser taken on the line II--II of Fig. l; and

Fig. 3 is an enlarged cross-sectional view through a modified form ofmy-invention.

'I'he circuit interrupter shown in Fig. 1 to illustrate the invention isa high voltagev expulsion fuse. The main fuse tube 5 is of fibre or abrous material impregnated with a phenolic condensation resin. Thisinsulating tube is threaded at eeen end, andv is provided at its upperend with a contact ferrule 6, and at its .lower end with a contactferrule 1. The fibrous insulating tube 5 is protected against theweather when used out of doors by an outer tube 9 of refractoryweatherproof material, such as glass or porcelain. The outer refractorytube 9 is supported through gaskets Il Vbetween the ends of the tube andthe inner ends of the contact fer- 10 rules 6 and 1.

Positioned within the fibre tube 5 at its lower end is a removable renllhaving a nbre tube i3 on one end of which is threaded a terminal ferruleI5. Inside of the nbre tube Il of the renll,

there is a lining I1 of arc extinguishing material which is preferablysolid boric acid (H3303) which when acted upon by an arc is decomposed,giving on water vapor (H2O), leaving solid boric oxide (B203) Othermaterials may be used which give oil.' a large quantity of a gas whichis readily cient size to substantially close the upper end of thepassage. The lower-end of the conducting member 2l is connected to afusible element 2l which may be provided with a strain wire 2l torelieve the fusible element fromv tension. 'I'he lower end of thefusible element and the strain wire are fastened to the contact ferruleII on the Kend of the renll. A nbre disc 2l, which is secured in the endof the refill ferrule il with a driven nt, is blown out as soon as avery small pressure has built up in the arc passage il and is largelydestroyed by the blast of hot gas.

'I'he upper end of the conducting rod 2i is removably connected to atension spring 21, which is fastened at its other end to the uppercontact ferrule I. A nexible conducting shunt 2l conducts current to theconducting rod 2l from the upper terminal 8. The detailed constructionof the removable renll and the spring, together with the means by whichit is removably positioned within the outer tube, is similar to theconstruction shown in Rawlins Patent No. 1,976,634, issued October 9,1934, to the assignee of this invention, and it is, therefore, notnecessary to describe it in detail here.

The renll unit is also provided with an auxiliary arc passage 3l havinga secondary fusible element 33 arranged so that heavy current arcs willbe nnally extinguished in the main arc passage Il and small current arcswill be nnally extinguished in the smaller auxiliary arc passage 3l.'I'he .details of this structure and its method of operation are alsofully described in Rawlins Patent No. 1,976,634.

'I'he lower contact ferrule 1 is internally threaded at its lower end toreceive the cooling chamber or condenser 34. 'I'his condensercomprises aportion of steel tubing 35 having an end plate 31 welded to close itslower end. The upper end of the tube 35 is threaded to receive a plug llwhich has an opening into which is threaded a connecting collar l I. Theupper end of the collar is threaded to be screwed into the lower end ofthe terminal ferrule 1. A pin Il locks the tube 35, the plug 39 andthecollar Il together so that the condenser may be unscrewed from theterminal ferrule 1 to permit the renll containing the fusible element tobe removed and replaced after each operation of the fuse.

Inside of the chamber formed by the tube 3l. there is positioned a massof cooling material which may be provided in any one of a number ofdifferent forms. The cooling material has a multiplicity of intersticesproviding a large area 0f surface with which the arc products maycontact to be cooled and deionized. It is an important feature of theinvention to provide this mm of cooling material with a central openingin alignment with the open end of the arc passage so that the gasesflowing expulsively out of the arc passage will not be substantiallyobstructed and may flow into the center of the mass oi' coolingmaterial. By making the opening in the mass of cool- `lng materialtapered, the smaller free area through which the gas may now at thesmaller end of the opening forces the gas to now into the interstices inthe cooling material and be uniformly distributed therein. The fact thatthe opening in the mass of cooling material is tapered also has theadvantage that a greater mass of material may-be provided than where theopening is of a uniform width which must be large at its end adjacentthe end of the arc passage in order to not unduly obstruct the expulsivenow of gas.

The drawing shows one preferred form of cooling means in the chamberwashers or plates 45 which three brass tubes 41. The washers are ofcopper or other material having a high specific heat and a high rate ofheat conduction. The washers or plates are spaced apart by small washers40 between the plates. The ends of the brass tubes 41 are riveted orspun over so that the stack of plates is held together and may bepositioned in the chamber as a single unit.

Eachof the plates or washers I5 is provided with a central opening Il,which has a large area in the plates at the end of the condenser nearestthe end of the arc :e: eil.. By making the opening-through these platesof large area, there is very little obstruction to the gases nowing outof the end of the arc e. The holes in the upper plates. should have anarea as large as the major part of' the area of the lower enlarged endof the arc passage il or several times the crosssectional area of theupper restricted end of the pe i9. The size of the openings through theplates or washers 45 is restricted at intervals along the stack untilthere is only a small opening at the closed end of the chamber.

As shown in Figs. 1 and 2, there are six dinerent groups of plates withthe openings of the same size in each group, whereas in the modincationshown in Fig. 3, the openings through the plates taper uniformly fromthe end of the condenser adjacent the arc passage to the other end ofthe condenser. The uniform taper shown in Fig. 3 is theoretically moredesirable, but it has been found that the stepped arrangement shown inFig. 1 gives almost as good results and is more desirable from amanufacturing standpoint, since fewer different parts are required, thusreducing the cost.

The operation of the circuit interrupter of my invention is as follows:When an overload occurs, the fusible element 2J and the strain wire 25are melted so as to permit the tension spring 21 to pull back theconducting are 'drawing member 2l or if my invention is used in acircuit breaker, the conducting rod 2| has a moving contact on its lowerend which is drawn away from a nxed concomprising a stack of areassembled upon tact connected to the ferrule I l. In either case,

the arc is initially established in the large tapered portion of the arcpassage Il and is then drawn back into the more restricted portion ofthe passage. The arc acts upon the arc extinguishing material I1 alongthe passage which gives oi! a large quantity of gas. While a solidmaterial such as boric acid is shown for supplying the arc extinguishinggas, the device may also contain a liquid which will give o!! gas whenacted upon by the arc.

The arc drawing rod 2| substantiallycioses the upper end of the arcpassage I9 and thereby causes the gases formed to ilow out of the lowerend of the passage. The restricted passage causes the gas given of! -toquickly reach a high pressure and iiow expulsively through the arc toAcarry away the hot ionized arc products.

The fact that .the cooling members in the condenser have a large passageat the end of the condenser nearest the arc passage permits the gases toiiow freely from the open end of the arc passage without substantialobstruction. 'I'his makes it possible to take full advantageof theexpulsion action ofthe flowing gas to quickly extinguish the arc.

The use of plates having openings of decreasing size along the stackpermits the edge of each plate which projects beyond the edges of theplates above to act as a deilector which catches the outfiowing gas andmakes use of the forward motion of the gas to deflect it into the spacesbetween the plates as indicated by the flow lines B3 in Fig. 3. Thisgives a uniform distribution of the outflowing gas among all of theplates as soon as the gas begins to flow andgreatly increases the rateat which the gas is condensed so that it may be condensed almost as fastas it is formed. This keeps the internal pressure in the condenser to aslow a value as possible and makes it possible to increase the eiliciencyof the arc extinguishing action, since the'expulsive ilow of gas throughthe arc passage is not substantially interfered with.

While I have shown and described in detail certain preferred forms of myinvention, it is contemplated that various modifications may be made andit is` intended that the claims shall cover such modifications. Where itis stated that the arc passage is open or is normally open at one endduring the extinguishing of the arc, it is intended to includestructures wherein there is a cover over the end of the arc passagewhich is blown open as soon as a small pressure is built up so thatthere will be an open end passage through which the gases can flowexpulsively, except perhaps during the interruption of the smallestcurrents which may not require an expulsion action for theirinterruption. Also, where it is stated that the condenser issubstantially enclosed, it is contemplated that some type of safetyvalve may be provided which would open up when veryhigh pressures arereached to prevent bursting of the chamber. With such an arrangement,the condensing chamber would still be entirely enclosed when operatingover the range of currents which the device is normally intendedto-interrupt.

I claim as my invention:

l. In a circuit interrupter, means for establishing an arc and causing aow of gas, a chamber for receiving said gas, material in said chamberhaving a large area of surface with which said gas may contact, meansproviding a passageintosaidmateriaiinthechamberofsufflcient size at theend nearest the point where the arc is established to permitsubstantially free ow of the gas into said material, and means atintervals along said passage projecting into the passage beyond the partof said material directly ahead thereof for deflecting the gas into saidmaterial.

2. In a circuit interrupter, means for establishing an arc and causing aow of gas, a chamber for receiving said gas, material in said chamberhaving a large area of surface with which said gas may contact, meansproviding a passage into said material in the chamber of suilicient sizeat the end nearest the point where the are is established to permitsubstantially free flow of the gas into said materiaL, and said passagebeing progressively restricted.

3. In a circuit interrupter, a restricted arc massage, means' forestablishing an arc in said restricted passage, means for causing fluidto flow expulsivelythrougn the restricted passage and out one endthereof, achamber positioned over said end of the arc passage, saidchamber being entirely closed when normally interrupting the circuit andhaving cooling means therein with a multiplicity of intersticesproviding a large surface area, and a progressively restricted openingextending from said end of the arc passage into the cooling means. y

4. In a circuit interrupter, a restricted arc passage, means forestablishing an arc in said restricted passage, means for causing fluidto ilow expulsively through the restricted passage and out one endthereof, a chamber positioned over said end of the arc passage, saidchamber being entirely closed when normally interrupting the circuit andhaving cooling means therein with a multiplicity of intersticesproviding a large 'surface area, a progressively restricted openingextending from said e'nd of the arc passage into the coolingv means, andsaid progressively restricted opening having an area through which thefluid may flow at its end adjacent said restricted passage not less thanone-half of the area of said end of the restricted passage.

5. In a circuit interrupter, means forA establishing an arc and causinga flow of gas, a chamber for receiving said gas, material in saidchamber having a large area of surface with which said gas may contact,said material having a 1- central opening therethrough of sufficientarea to accommodate substantially the full flow of said gas at the endof the chamber next to the means for establishing the arc and havingportions along its length projecting into the opening a distance beyondthe corresponding portions nearer to the means for establishing the arcfor receiving said ilow of gas and directing it laterally into thematerial.

l6. In a circuit interrupter, means for establishing an arc andcausing'a flow of gas, a chamber for receiving said gas, said chamberbeing substantially entirely enclosed during normal operations of theinterrupter to open the circuit, a plurality of spaced metallic platesin said chamber, said plates nearest the means for establishing the archaving openings therethrough of suflicient area to accommodate the fulliiow of said gas, and said plates at more remote points having openingsof smaller area.

'7. In a circuit interrupter, a passage for the arc, means forestablishing an arc in said passage, means providing fluid to iiowexpulsively through the passage and out one end thereof, a normallyclosed chamber positioned over said end of the arc passage, a mass ofcooling material in said chamber having a multiplicity of smallinterstices, said mass of cooling material having a large centralopening therein in alignment with said passage for the arc to permitsaid fluid to ow into the center of the mass of cooling material withoutsubstantial obstruction and said large central opening being taperedtoward the end of the chamber opposite the end of the arc passage forcausing the fluid to be forced to flow into the` small interstices inthe mass oi' cooling material.

8. In a circuit interrupter, means between which an arc may play, meansalong the path of the arc which when acted upon by the are gives ofi' alarge quantity of gas which is condensable at room temperatures, acondenser for receiving said gas, said condenser having a mass ofcooling material with a passage therein which is large at the end wheresaid gas is ilrst received and which'is reduced in size at a pluralityof points toward the other end.

9. In a circuit interrupter, means for establishing an arc, a restrictedpassage ior the arc which is open at one end, a material along thepassage which gives off a readily condensable gas when acted upon by thearc to flow through the passage and out its open end with an expulsionaction, a closed condenser positioned over the open end of said passage,said condenser including a mass of material having an opening extendingthereinto from its end nearest the open end of said passage, saidopening having a sufllciently large cross-sectional area at its endnearest the open end of said passage to permit the gas to ilow thereintowithout substantial obstruction, and means at intervals along theopening for causing the gas to be deflected into the mass of material.

10. In a circuit interrupter, a movable conducting rod for drawing thearc, a restricted passage into which said rod extends and in which thearc is drawn, said passage being open at one end at least during part ofthe time that the arc is being extinguished and during at least a partoi' the same time being substantially closed at the other end by saidconducting rod, material along said passage for giving oil gas whenacted upon by the arc, a chamber on the open end of said passage forreceiving said gas, said chamber having means therein providing a largearea oi.' surface with which the 'gas may come in contact, a passage forthe gas in said means in the chamber, said passage for the gas having across-sectional area at its end nearest the arc passage at least severaltimes the cross-sectional area oi' the portion of the arc passage whichis substantially closed by the conducting rod, and said passage for thegas decreasing in cross-sectional area as its other end is approached.

11. In a circuit interrupter, a movable conducting rod for drawing thearc, a restricted passage into which said rod extends and in which thearc is drawn, said passage being open at one end at least during part ofthe time that the arc is being extinguished and during at least a partof the same time being substantially closed at the other end by saidconducting rod, material along said passage which when acted upon by thearc gives ofi.' gas substantially all of which is condensable `at roomtemperatures, a substantially closed condenser over the open end of saidpassage and into which the gas may ilow with an expulsion action, saidcondenser having therein a mass of metallic material having amultiplicity of interstices providing a large area o1' surface forcooling and condensing the gas, said mass of metallic material having anopening extending thereinto for receiving the gas, said opening having across-sectional area at its end nearest the arc passage which is severaltimes the cross-sectional area of the portion of the arc passage whichis substantially closed by the conducting rod, and the cross-sectionalarea of said opening being progressively restricted toward its otherend.

JAMES M. WALLACE.

